Area measuring machine

ABSTRACT

Wheel type electronic sheet material area measuring machine comprises means for emitting a test start signal, operated either manually or automatically at a particular point in the machine cycle, and test means actuated by the test start signal to cause material detecting means associated with each wheel to emit a signal normally indicating presence of sheet material for a predetermined length of travel of a conveyor surface on which the material is normally supported, the wheels running on the conveyor surface. Thus each of the signalling means associated with the wheels should, if the machine is operating correctly, emit a number of test signals. The signals emitted by the signalling means of each wheel of a group of wheels are added and compared with an acceptable range of numbers of test signals which would be emitted in respect of that group if the machine is functioning within the predetermined tolerances. A warning is given if any of the groups of wheels are not within the predetermined tolerances and the machine is prevented from measuring area until functioning correctly. Preferably similar tests are run in respect of small groups of wheels e.g. ten and in respect of a group consisting of all the wheels, e.g. overall machine accuracy.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is concerned with improvements in or relating to areameasuring machines.

2. Prior Art

In the complete specification of U.S. Pat. No. 3,717,414, issued Feb.20, 1973 U.K. Pat. No. 1,446,866, are described area measuring machinescomprising (a) support means, e.g., a roller, for supporting sheetmaterial the area of which is to be measured and for feeding thematerial through the machine, (b) a plurality of wheels disposed side byside across the machine and arranged to run on the roller or on sheetmaterial fed by the roller past the wheels, (c) detecting means, oneassociated with each wheel, for detecting the presence of a piece ofsheet material fed between the wheel and the roller, (d) signallingmeans for signalling each time the periphery of a wheel has been rotatedthrough a unit distance by the passage of sheet material therepast and(e) computing means for summing the signals from each wheel to indicatethe area of the piece of sheet material.

Such machines have been found to be, in operation, reliable andaccurate. However, should a fault develop on a machine such as describedin the aforementioned patent specifications, it is difficult to notice.In order to test that such machines are operating satisfactorily it is aknown practice to feed a piece of leather of known area through themachine a number of times, and check that the area of the pieceregistered by the machine is within the permitted tolerances.

One of the various objects of the present invention is to provide animproved area measuring machine in which it is possible readily to checkthat the machine is operating satisfactorily.

BRIEF SUMMARY OF THE INVENTION

The invention provides in one of its various aspects an area measuringmachine comprising (a) conveyor means comprising a conveyor surface forsupporting sheet material the area of which is to be measured and forconveying the sheet material through the machine in the operationthereof, (b) a plurality of wheels disposed side by side across themachine and arranged to run on sheet material conveyed to the conveyormeans or, in the absence of sheet material, on the conveyor surface, (c)detecting means, one associated with each wheel for detecting thepresence of a piece of sheet material between the wheel and the conveyorsurface, (d) signalling means for signalling each time the periphery ofa wheel has been rotated through a unit distance and for emitting asignal to be summed should the output from the detecting meansassociated with that wheel indicate that a piece of sheet material ispresent between the wheel and the conveyor surface, (e) computing meansfor summing the signals from each wheel to indicate the area of thepiece of sheet material, (f) means arranged to emit a test start signal,and (g) test means actuated by the test start signal, to cause (in theabsence of sheet material) all of the detecting means to emit a signalwhich would normally indicate the presence of sheet material, for apredetermined length of travel of the conveyor surface such that each ofthe signalling means associated with the wheels of a group of wheelsshould the machine be functioning correctly emits a number of testsignals. The test means comprises a test circuit including a comparatorby which the total number of test signals emitted by the signallingmeans of said group of wheels is compared with an acceptable range ofnumbers of test signals which would be emitted in respect of said groupsof wheels when the machine is functioning within predeterminedtolerances. The test means is constructed and arranged to indicate whenthe comparator signals that the total number of test signals emitted bythe signalling means of said group of wheels is not within theacceptable range of numbers of test signals.

Preferably the conveyor means comprises a roller which provides theconveyor surface for supporting sheet material.

Preferably each detecting means of a machine of the present inventioncomprises a first detector equally spaced from next-adjacent firstdetectors and arranged at one side of the path of travel of the sheetmaterial through the machine, to detect a beam of radiation directedtheretowards from a first radiation source arranged at the other side ofthe path of the sheet material so that the presence of sheet materialbetween the wheel and the conveyor surface breakes the beam ofradiation. Conveniently each first detector is a photoelectric cell andeach first radiation source is a source of light; suitably a singleradiation source is arranged to direct a beam of radiation at all of thefirst detectors. Preferably the first radiation source is rich in infrared radiation and, where a single first radiation source is used todirect a beam of radiation at all of the first detectors, the firstradiation source is a light tube of the type known as an "architecturaltube" which has a filament extending the length thereof.

Preferably where the first radiation source is a source of light and thefirst detectors are photoelectric cells. The conveyor means comprises aroller which is transparent to the radiation, for example a glassroller; preferably the glass roller is provided by a glass tube and thesource of light is mounted inside the glass tube to direct a beam ofradiation at the first detectors.

Preferably each of the wheels comprises a rim portion projectinggenerally parallel with the axis of rotation of the wheel from theremainder of the wheel. Preferably, in this case, where the firstdetectors are first photoelectric cells each first detector is mountedon means by which the wheel is supported within the radius of the rimportion and the rim portion is continuous and transparent to the infrared radiation emitted by the first radiation source, the firstphotoelectric cells being operated by the infra red radiation.Preferably in this case the signalling means of the invention comprisesecond radiation detectors, one associated with each wheel, mounted onmeans for supporting the wheel within the radius of the rim portion atone side of the rim portion, and a second radiation source mounted atthe opposite side of the rim portion to direct a beam of radiationtowards the second detectors. In this case the wheel preferablycomprises alternate first and second portions, for example provided by anotched insert ring fitted in the rim portion, arranged so that as thewheel rotates the notched insert ring also rotates and intersects thebeam of radiation from the second source. The material of the insertring is opaque to the radiation emitted by the second radiation source(which is also preferably a source of light rich in infra red radiation,suitably an architectural tube) so that when one of the notches in thenotched ring intersects the beam, radiation from the second sourcereaches the second detector but when the ring itself intersects thebeam, radiation from the second source is prevented from reaching thesecond detector. The notches are so spaced apart that as the wheelrotates the distance moved by the running surface of the rim portion ofthe wheel from the point at which one of the notches intersects the beamof radiation from the second source permitting it to reach the seconddetector associated with the wheel (i.e. the notch is aligned betweenthe second source of radiation and the second detector) to the point atwhich the next adjacent notch in the notched ring intersects the secondbeam of radiation and again permits the second beam to reach the seconddetector, is the unit distance. Thus the notched ring effectivelydivides the running surface of the rim portion into alternate first andsecond portions, the centers of the first portions of the runningsurface being equally spaced apart so that when one of the firstportions of the running surface intersects the beam radiation from thesecond source reaches the second detector, but when one of the secondportions of the running surface intersects the beam, radiation from thesecond source is prevented from reaching the second detector. Rotationof the wheel thus causes a pulse representing unit area to be generatedby the signalling means each time the rim portion of the wheel hasrotated through the unit distance, the pulse being emitted by thesignalling means to be summed by the computing means for summing thesignals when the first detector associated with that wheel indicates thepresence of sheet material between the wheel and the conveying means.

The means arranged to emit a test start signal may be manually operated,for example by an operator pushing a test button at an appropriate time,or may be operated automatically at a predetermined point in theoperation of the machine. Where the means arranged to emit a test startsignal is operated automatically the means may be automatically operatedafter a predetermined number of pieces of sheet material have beenpassed through the machine; this number may be set by the operatorbefore commencing to use the machine and may conveniently be such thatthe test start signal is emitted at the end of each batch of pieces ofmaterial fed through the machine.

Preferably, the detecting means comprises first detectors of radiationarranged to detect a beam of radiation directed theretowards by a firstradiation source arranged at the opposite side of the path of travel ofsheet material through the machine, the test means causes all of thedetecting means to emit a signal which would normally indicate thepresence of sheet material by switching off the first radiation sources(or source where a single source directs a beam of radiation towards allof the first detectors). In many instances, for example where the firstradiation source is an architectural tube, the first radiation sourcedoes not cease to emit radiation immediately, it is switched off and thetest means comprises a time delay in these cases to allow the level ofradiation to fall sufficiently to not operate the first detectors. Wherethe first radiation source is mounted within a glass tube, thepredetermined length of travel of the conveyor surface is determined bythe test means causing the test signals to be emitted for a suitablenumber of revolutions of the glass tube. Glass tubes, although allnominally of a similar diameter, may not all be precisely the same andthus each glass tube must be calibrated to enable the test means todetermine the predetermined length sufficiently accurately. The glasstube may therefore comprise means, e.g. comprising a metal block securedto the tube and a proximity switch operated by the block as the tuberotates, by which start and stop signals are generated in the test meansto indicate the predetermined length of travel of the conveyor surfaceof the glass roller.

In a machine constructed in accordance with the present invention, thegroup of wheels may consist of all of the wheels of the machine or mayconsist of less than the total number of wheels in the machine. The testmeans preferably comprises a first comparator by which the total numberof test signals emitted by the signalling means of a group of wheelsconsisting of all of the wheels of the machine is compared with a firstacceptable range of numbers of test signals, and a plurality of secondcomparators, each associated with a group of wheels (for example, 10)the total wheel of the machine being divided into a number of suchgroups of equal size, by which the total number of test signals emittedby the signalling means of each such small group of wheels is comparedwith a second acceptable range of numbers of test signals. The machinepreferably includes a first indicator which indicates whether or not thetotal number of test signals received by the first comparator is withinthe first acceptable range and a number of second indicators, oneassociated with each of the smaller groups of wheels, to indicatewhether or not the total number of test signals received by each secondcomparator is within the acceptable range.

Conveniently, the test means is arranged to be operated at the end ofeach batch of pieces of sheet material, for example, fed through themachine. Preferably the test means is arranged to cause the tests torecycle until the fault indicated has been removed.

Reference is hereby directed to our co-pending patent application Nos.010,134, filed Feb. 7, 1979 and 010,133 filed Feb. 7, 1979 for dicussionof other testing facilities which are preferably included in a machinein accordance with the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other of the various objects and several aspects of thepresent invention will become more clear from the following description,to be read with reference to the accompanying drawings, of an areameasuring machine. It will be realized that this area measuring machinehas been selected for description to illustrate the invention by way ofexample and not by way of limitation of the invention.

In the accompanying drawings:

FIG. 1 is a front view, with parts broken away, of the illustrativemachine;

FIG. 2 is a side view, partly in section of parts of the illustrativemachine showing a wheel and a roller thereof;

FIG. 3 is a view in section on the lines III--III of FIG. 2, of a wheeland support member of the illustrative machine;

FIG. 4 is a perspective view of a wheel of the illustrative machine;

FIG. 5 is a diagrammatic view showing electrical circuitry and printedcircuit boards of the illustrative machine indicating electricalconnections in a general manner;

FIG. 6a is a view showing electrical circuitry mounted on each supportmember of the illustrative machine;

FIG. 6b is a diagrammatic view showing electrical circuitry of an inputboard of the illustrative machine;

FIG. 7 is a diagrammatic view showing electrical circuitry of a scanboard of the illustrative machine;

FIG. 8a is a diagrammatic view showing electrial circuitry of a controlboard of the illustrative machine;

FIG. 8b is a diagrammatic view showing a display unit of theillustrative machine;

FIG. 9 is a diagrammatic view showing electrical circuitry of a testboard of the illustrative machine; and

FIG. 10 is a diagrammatic view showing electrical circuitry of anauxiliary board of the illustrative machine.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The illustrative area measuring machine is generally similar inconstruction and design to the machines described by way of example inthe aforementioned U.S. Pat. No. 3,717,414 issued Feb. 20, 1973 and U.K.Pat. No. 1,446,866 and reference is hereby directed to theaforementioned patent specifications for further information on aspectsof the illustrative machine not described herein in detail.

The illustrative area measuring machine comprises a frame 10 on which ismounted a horizontal feed table 12 extending the width of the machine. Aglass roller 14 is mounted for rotation about a horizontal axisrearwardly of the feed table, with an upper portion of the rollerpositioned so as to receive sheet material, for example, hides H, theareas of which are to be measured, fed rearwardly on the feed table 12by an operator. A plurality of identical wheels 46 are disposed side byside across the machine and are mounted for rotation about horizontalaxes parallel with the axis of the glass roller 14. The wheels 46 reston the glass roller 14 when no material is being fed through themachine.

The glass roller 14 is driven to rotate it about its axis in theoperation of the machine by an electric motor (not shown) through adrive belt 38 passing around a pulley 17 at an end portion of the glassroller. The speed of the motor is adjustable so as to adjust thethroughput speed of sheet material between 18 meters a minute and 25meters a minute.

The wheels are carried by an arrangement of support members 58. Each ofthe support members 58 is identical, and for convenience, only one willbe described hereinafter. The support member 58 is injection molded ofplastic material and comprises an arm portion 60 and at one end of thearm portion, a cowl portion 62, as shown in FIG. 2. The cowl portion 62comprises an end plate 64 which is disposed vertically when the supportmember is mounted in the machine and, projecting from this end plate, awall 66 having a cylindrical inner surface. A metal axle pin 70 projectsat right angles from an inner surface 68 of the end plate 64, as shownin FIG. 3, and lies axially of the cylindrical inner surface of the wall66. The axle pin 70 is incorporated in the plastics portion of thesupport member 58 during the molding thereof. The axle pin 70 and wall66 project from the end face 64 of the cowl portion in the samedirection. The height of the wall 66 above the inner surface 68 of theend plate 64 is the same along the whole of the wall and the same as thelength of the axle pin 70 above the inner surface 68. Thus an outer endportion of the axle pin 70 and a rim portion of the wall 66 remote fromthe end plate 64 lie in a plane. Clip members 74 and 76, as shown inFIG. 2, project inwardly from the inner surface 68 of the end plate 64,a first, lower, clip member 76 being disposed on a lower portion of thewall and the second clip member 74 being disposed at a position where aline from the clip member 74 to the axle pin 70 makes a right angle witha line from the clip member 76 to the axle pin 70. The clip members 74and 76, are spaced from the inner surface of the wall 66, the lower clipmember 76 projecting further than the other clip member 74, as shown inFIG. 3.

A plurality of rods 80 are supported coaxially by a number of brackets82 projecting rearwardly from a front portion of the frame 10. The armportions 60 are generally U-shaped, as shown in FIG. 2, and comprise aboss 86 at the end portion of the arm portion 60 remote from the cowlportion 62, the boss 86 being received on one of the rods 80 so that thesupport members 58 can pivot about the rods 80. Each of the rods 80 isof such length as to accommodate a group of ten support members 58 (withthe bosses 86 in contact). Each of the rods 80 can readily be liftedclear of its support brackets 82 so that for maintenance purposes groupsof ten support members can readily be removed from the machine. Thesupport members 58 are supported by the rods 80 so as to projectrearwardly from the rods 80. A gap 88, as shown in FIG. 2, is formed ina lower portion of the wall 66 and the gap 88 extends round to justbeyond the clip member 74.

Each of the wheels 46 is, as hereinbefore mentioned, identical and onlyone wheel will therefore be described. Each wheel is injection molded ofa plastics material which is opaque to visible light but transparent toinfra red radiation. Each wheel 46 comprises a central boss 48, as shownin FIG. 2, connected by a web portion 50 (to which a metal disc 106 issecured, to weigh the wheel/support member assembly) to a rim portion 52having a cylindrical, outer, running surface, the rim portion beingcontinuous and having no holes therein. Each wheel further comprises anotch ring 53 slidingly received within the rim portion 52 and securedthereto, as shown in FIGS. 2-4, the notch ring extending acrossapproximately half the axial width of the rim portion 52. The notch ring53 is injection molded of a plastics material which is opaque both tovisible light and infra red radiation. Notches 56 are equally spacedaround the notch ring. A radial line drawn from the axis of rotation ofthe wheel 46 on the axle pin 70 through the center of a notch 56intersects the running surface of the rim portion at a position spaced aunit distance (in the case of the illustrative machine 20 mm) from theposition at which a radial line drawn from the axis of rotation throughthe center of the next adjacent notch 56 intersects the running surfaceof the rim portion. Thus the running surface of the wheel 46 can beconsidered to be divided by the notches 56 into 20 mm circumferentiallengths. Each of the wheels 46 is mounted for rotation on one of theaxle pins 70 projecting from the end plate 64 of one of the supportmembers 58, the axle pin being received in a hole in the boss 48 of thewheel 46. The wheels 46 are each retained on the pins 70 by a circlip71. The cowl portion 62 of each support member 58 is such that the wall66 thereof shrouds the rim portion 52 of its associated wheel except ata lower end portion where the rim portion 52 projects through the gap 88in the wall. The first and second clip members 76,74 are thus enclosedin a space bounded by the rim portion 52, the web portion 50 of thewheel and the end plate 64 and wall 66 of the cowl portion 62 of thesupport member. A lower, first photoelectric cell 94 is mounted in theclip member 76 with its light receiving portion directed downwardlytowards the gap 88 in the wall 66. The rim portion 52 of the wheel liesradially outwardly of the lower photoelectric cell 94 and the lightreceiving portion is directed towards the rim portion of the wheel clearof the notch ring 53 and towards a lower light source e.g., a light tube26. A second photoelectric cell 92 is held by the clip member 74 with alight receiving portion directed towards the gap radially outwardly in adirection at right angles to that of the first cell 94. The cell 92 isaligned with the notch ring 53 and the notches 56 in the notch ring 53are so positioned as to move on a path (when the wheel 46 is rotated)which intersects a line drawn between the light receiving portion of thesecond photoelectric cell 92 and an upper light source, e.g., a lighttube 108. The photoelectric cells 92 and 94, are connected by wires 130and 134, as shown in FIG. 2, to an input board 133, as shown in FIGS. 5and 6. The photoelectric cells 92 and 94, are of a type sensitive toinfra red radiation as well as visible light and respond rapidly tolight.

The mounting of the photoelectric cells 92 and 94, between the webportion 52 of the wheel and the end plate 64 of the cowl portion 62gives protection to the cells 92 and 94, against contamination by dust.The cowl portion 62 (which is opaque both to visible light and infra redradiation) also minimizes the risk of stray radiation reaching the cells92 and 94, and activating them to cause false area indicating pulses tobe recorded by a computing device of the illustrative machine. Themounting of the photoelectric cells 92 and 94, (and associated lightsources 108 and 26) at right angles to one another minimizes the risk oflight from the upper light source 108 activating the cell 94 or lightfrom the lower light source 26 activating the cell 92 or of reflectedlight activating the cells. The construction and arrangement of themachine is such that when the support members 58 are mounted on anassociated rod 80, the axle pins 70 are horizontal and parallel with theaxis of rotation of the glass roller 14, the axle pins 70 also lying onthe axis of the cylindrical running surface of the rim portions 52 ofthe wheels 46.

The glass roller 14, as hereinbefore mentioned, is supported forrotation in bearings (not shown). A steel tube 22 mounted on the frame10 passes through the bearings and lies with its axis on the axis ofrotation of the glass roller 14. The steel tube 22 has a slot 25extending along its length between the end supports and facing upwardly.The light tube 26 is mounted in the steel tube 22 in such a manner as toillustrate the whole of the slot 25. The slot 25 is so positioned thatlight emitted by the light tube 26 passing through the slot 25 isdirected towards the first photoelectric cells 94. The light tube 25 isof the type known as an "architectural tube" and has a filamentextending the length thereof. The light emitted by the tube 26 isrelatively rich in infra red radiation which readily penetrates theplastic of the rim portion 52 of the wheels 46 to reach the firstphotoelectric cells 94.

The support members 48 when mounted on the rods 80 as hereinbeforedescribed cause the first photoelectric cells 94 to be evenly spacedapart across the illustrative machine, the spacing preferably being 25mm.

Every other one of the wheels 46 and support members 58 has a strikerarm 102 associated therewith, as shown in FIG. 2. Each arm 102 has alightly spring-loaded end portion (not shown) as a push-fit over theboss 48 of the associated one of the wheels with the striker arm betweenthe web portion 50 of the wheel and the end plate 64 of the associatedone of the support members 58. The degree of friction between the innerend of the striker arm 102 and the boss 48 of the wheel 46 may beadjusted by a screw (not shown) and is such that when the wheel rotatesin the through feed direction little braking force is applied to thewheel; the arm is prevented from rotating as the wheel rotates byengagement with the clip member 76. However, should the wheel be rotatedin the direction opposite the through feed direction the arm 102 will berotated towards a microswitch 78 secured to the inner surface 68 of theend plate 64 of each of the support members 58 and thereby operate themicroswitch 78 to cause an alarm signal to be transmitted to theelectrical circuitry.

The plastics material of which the wheels are formed is such that thereis little or no frictional drag between the bosses 48 and supportmembers 58. The wheels are weighted to ensure that they rest (whenmaterial is not passing through the machine) with the running surface incontact with the glass roller 14. When the wheels 46 are in contact withthe glass roller, the axle pins 70 are, as hereinbefore mentioned,coaxial.

The light tube 108 is mounted in the machine between the rods 80 and thecowl portions 62 of the support members 58. The light tube 108 is anarchitectural tube of similar type to the tube 26. The light tube 108 ismounted in a metal tube 110 in which a slot 114 is out in a side portionextending across the illustrative machine parallel with the rods 80, asshown in FIG. 2. The slot 114 is disposed in alignment with thephotoelectric cells 92 on the support members 58 so that when one of thenotches 56 in the notch ring 53 of one of the wheels 46 is in alignmentwith the light receiving portion of the photoelectric cell 92 associatedwith that wheel, light from the light tube 108 shines through the slot114 and the notch 56 onto the light receiving portion of thephotoelectric cell.

A metal chute 116, as shown in FIG. 1, is mounted on a rear portion ofthe frame 10 so that material fed between the wheels 46 and glass roller14 from the front in the operation of the machine is deflecteddownwardly and then forwardly by the chute 116 so that the materialleaves the machine through an opening in the lower front portion of themachine beneath the feed table 12.

The machine also comprises scraper means (not shown) so arranged thatskins fed through the machine still adhering to the glass roller 14 whenthey reach the scraper means are scraped by the scraper means from thesurface of the roller 14 and fall into the chute 116.

A felt pad (not shown) may be provided extending the length of the glassroller 14 (clear of the light tube 26) bearing on the roller 14 to wipethe glass roller as it rotates to remove dirt from the roller so thatpassage of light through the roller 14 is not impeded and the risk ofdirt being transferred to the leather is reduced.

The electrical circuitry of the present invention is hereinafterdescribed diagramatically with reference to FIGS. 5-10 of theaccompanying drawings. In FIG. 6a is shown electrical circuitry which ismounted on each support member 58 but for convenience the circuitryassociated with only one of the support members is shown in FIG. 6a. Thefirst photoelectric cell 94 (of detecting means of the machine) has anoutput line 130 connected to an input line 132 of an input board 133, asshown in FIG. 6b of the illustrative machine. The second photoelectriccell 92 (of signalling means) is connected by an output line 134 to asecond input line 136 to the input board.

There are sixty support members 58 and associated wheels 46 in themachine and each input board 133 has associated with it ten of thesupport members 58 and wheels. On the input board some of the circuitryis duplicated for each of the support members 58; for convenience onlyone set of this circuitry is shown in FIG. 6b, to the left of thechain-dot line.

In the operation of the machine a piece of leather H passing through themachine between one of the wheels 46 and the glass roller 14 willprevent light from the lower light source 26 reaching the firstphotoelectric cell 94 associated with that wheel. This will cause asignal to be sent on the line 130 to the line 132 to indicate thepresence of sheet material between that wheel and the roller 14. As thewheel rotates, with the running surface thereof running on the surfaceof the leather as it feeds between the wheel and the glass roller, thenotches 56 intersect the beam of light from the light tube 108 and causelight from the tube 108 to fall on the second photoelectric cell 92 in aseries of pulses, each of which indicates that the running surface ofthe wheel 46 has moved through the unit distance (20 mm in the case ofthe machine). The pulses thus generated are transmitted on the line 134to the line 136.

As hereinbefore mentioned the machine comprises six input boards, eachof which having ten input circuits similar to the circuit shown to theleft of the chain-dot line in FIG. 6b. In order to count the pulsesgenerated by all of the wheels, without losing a pulse, it is necessaryto ensure that the pulses reach counters 138 shown in FIG. 3a of themachine in an ordered serial format. In order to achieve this, themachine comprises a clock 140 as shown in FIG. 7, by which a circuitselector 142 is driven. The circuit selector 142 has a number of outputlines represented by the line 144 by which one of the six input boardsis selected, and a plurality of output lines represented by the line 146by which one of the input circuits (to the left of the chain-dot lineviewing FIG. 6b is selected. A clock output line 148 also leads from theclock 140. The clock output line 148 is connected to a clock input line150 of each input board. Each of the output lines 144 by which one ofthe input boards is selected is connected to a selector input line 152of the appropriate input board; thus the output line 144 is connected tothe selector input line 152 of the input board shown in FIG. 6b. Each ofthe output lines from the circuit selector 142 for selecting one of theinput circuits of an input board is connected to one of the input linesof all six input boards; thus the output line 146 is connected to thefirst circuit input line 154 of the input board shown in FIG. 6b. Theclock, selector, and circuit input lines 150,152 and 154, lead to aclock organizer 156 on the input board. In the operation of the machinethe circuit selector 142 selects one of the input board selector outputlines for example the line 142 and then runs through each of the circuitselector output lines in sequence and thus the clock organizer 156causes a clock pulse to be fed in sequence to each of the input circuitclock lines (of which a clock line 158 is representative) of that inputboard. The circuit selector 142 selects each of the input board selectoroutput lines in sequence and thus a clock pulse is fed on every inputcircuit clock line sequentially to every input circuit of each inputboard of the illustrative machine, synchronized by the clock 140.

As hereinbefore mentioned there are six input boards each having teninput circuits similar to that shown to the left of the chain-dot linein FIG. 6b; each of these input circuits operates in a similar mannerand for simplicity the operation of only one of the input circuits willbe hereinafter described. As the wheel 46 rotates causing pulses oflight to fall on the photoelectric cell 92 electrical pulses are emittedon the output line 134, to the input line 136 which leads to a pulseshaper 160; the pulses emitted on the line 134 have a guassian shapewhich is caused as the notch passes across the beam of light detected asthe photoelectric cell 92. The pulse shaper 160 shapes these pulses to asquare wave form. When the first, lower, photoelectric cell 94 detectsthat a piece of leather is passing between the wheel and the glassroller 14 a signal is emitted on the output line 130 to the input line132 and from the input line 132 on a read line 162 leading to the pulseshaper. At the same time the clock 140, circuit selector 142, and clockorganizer 156 cause clock pulses to be sent on the input circuit clocklines in a regular sequence. When a signal indicating that leather ispresent in the machine, is present on the read line 162 and a pulse isreceived from the photoelectric cell 92 on the input line 136 to thepulse shaper, the pulse is shaped to a square wave form but is inhibiteduntil the end of the pulse on the input line 136. When the end of thepulse on the input line 136 has been detected the next clock pulsereceived on the input circuit clock line 158 causes an output pulse tobe emitted from the pulse shaper 160 on the line 164; the output pulseis of the same shape and duration as the clock pulse generated by theclock 140. The output pulse on the line 164 passes through a latch 166and leaves the latch on a line 168 which is received by a ten-way "or"gate 170. There is one such ten-way "or" gate on each input board,arranged to receive pulses from each of the input circuits of that inputboard. When a pulse is received by the ten-way "or" gate, an outputpulse is delivered on a line 172 to a gate 174 which gives an areaoutput pulse on an output line 176 from the input board. Each inputboard has one such output line and each such output line is connected toa six-way "or" gate on a scan board 179 as shown in FIG. 5. Receipt of apulse by the six-way "or" gate 178 causes an area output pulse to beemitted on an output line 180. Because each of the pulse shapers 160 isscanned sequentially under the organization of the clock 140, circuitselector 142, and clock organizer 156 pulses can only be received by the"or" gate 178 sequentially, these pulses having the length and shape ofthe clock pulse and each pulse being spaced from the next pulse by atleast the interval between successive clock pulses (if no leather isbetween on of the wheels 46 and the roller 14, no pulse will be emittedin respect to the input circuit associated with that wheel and thus nopulse will be fed to the "or" gate 178). Area pulses on the output line180, as shown in FIG. 7, are fed through an area control 182 to a line184 leading to a gate 186 and from the gate 186 on an output line 188leading to an area input line 190 of a control board 191, (see FIG. 8a).The line 190 has a branch leading to a lamp driver 192, an output line194 from which leads to a pulsing indicator control 196 as shown in FIG.8b, by which an indicator lamp 198 on the display is caused to pulsateby the area pulses thus indicating that the area is being measured.

The area input line 190 of the control board also leads to a gate 200through a second gate 202 by which extra pulses may be introduced on aline 204 from an extra pulse control 206. The extra pulse control 206receives the area pulses from the line 190 and a switch 208 isassociated with the extra pulse control, as shown in FIG. 8a. The switchis adjustable by an operator in one percent steps to cause the extrapulse control 206 to make a percentage increase in the number of pulsesleaving the gate 202 on an output line 210 over the number of areapulses being fed to the control board on the area input line 190. Ifthis possibility of area input is not required, the gate 202, the extrapulse control 206 and the switch 208 may be omitted. When the extrapulse control 206 is fitted, the switch 208 is operated, according tothe type of leather which is being measured, to compensate for reducedarea measurements arising because of folds or wrinkles in the skin whichare impossible to eliminate as the skin is passed through the machine(but which will be eliminated during subsequent processing of theleather), the percentage increase being selected according to theaverage area not measured because of these wrinkles and folds.

The pulses received on the output line 210 are fed to a counter 212which counts the pulses and gives an output on a line 214 representingarea of leather in units of a quarter of a square foot, and to a counter216 which counts the pulses and gives an output on a line 218 indicatingarea in square decimeters.

It will be appreciated that each pulse on the area input line 190represents rotation of one of the wheels 46 by the unit distance of 20mm. As each wheel 46 is spaced from the next adjacent wheels by adistance such that the first, lower, photoelectric cells 94 associatedwith each of the wheels is spaced by 22 mm from the cells of thenext-adjacent wheels a pulse from one wheel represents an area of 500square mm. Thus each pulse received on the area input line 190 indicatesan area of 500 square mm. The output pulses on the line 210 representsthis area pulse any percentage increase in area fed in by the extrapulse control 206.

The lines 214 and 218, from the counters 212 and 216 lead to a unitselector 220. The unit selector 220 is set by the operator, beforemeasurement of area commences, by operation of a selector switch (notshown) which causes a signal to be fed on a line 222 to the unitselector 220 indicating whether the output is required in quarters of asquare foot or in square decimeters. An output is given from the unitselector on a line 224, as shown in FIG. 8a, which is connected to alamp driver 226, as shown in FIG. 8b, on the display to illuminate anappropriate one of lamps 228 to indicate on the display, to theoperator, the units in which the area is displayed. Depending on thesetting of the unit selector 220 an output from the unit selector 220 isgiven on the line 230, this output being the signals delivered on theline 214 or on the line 218 as determined by the setting of the unitselector. The output from the line 230, in FIG. 8a, is fed to thecounter 138 which gives binary counting decimal output on lines 232which are fed to memory decoders 234 on a display unit 235, as shown inFIG. 8b, the memory decoders driving light emitting diode displays 236to indicate the area measured. The smallest area displayed is onequarter of a square foot or 0.1 decimeters. The area outputs on thelines 232 are also fed to a memory of a printer which (when the end of askin is detected) prints the area on a piece of paper and sorts anaccumulated batch area total for a purpose to be discussed hereafter.

The machine of the present invention may be operated in one of twomodes, either manual or automatic. The machine is normally operated inautomatic and in this mode of operation the area of each skin isregistered and remains displayed by the display unit until the next skinis put into the machine, the display remaining for a slight period, upto a maximum of one second, after the next skin has been put into themachine. When another skin is put into the machine the counter 138 isreset (as described hereinafter) so as to display the area of the nexthide or skin after the delay previously mentioned. The machine isswitched from manual to automatic by insertion of a switch plug into asocket of the machine which causes a signal to be sent on a line 238 toa selector switch 240, as shown in FIG. 8a. Conveniently a foot operatedswitch is used when the machine is in manual; the foot switch is soarranged that when its plug is inserted in the aforementioned socket asignal is supplied on the line 242 to a gate 244 which prevents a signaltravelling on the line 246 reaching the line 248 and thus the signal isprevented from reaching the selector switch 240 so that no reset outputis given on the line 250 from the selector switch to the counter 138,the counters 212 and 216 and the extra pulse control 206. When themachine is in the manual mode of operation depression of the foot switchby the operator causes a signal to pass onto the line 248 therebyallowing a pulse to be supplied from a pulse generator 252 through theselector switch 240 to the line 250 to reset the counter 138 and thecounters 212 and 216, and the extra pulse control 206 to zero.

The machine further comprises means for detecting the presence of a skinor other piece of sheet material between one of the wheels 46 and theroller 14 in the operation thereof. The means for detecting the end ofthe machine utilizes the signal from the first, lower, photoelectriccell 94 on the input line 132 of the input board (as hereinbeforementioned each input circuit, of which there is one for each lowerphotoelectric cell 94, has an input line but for simplicity ofdescription only the input line 132 will be discussed hereinafter). Thesignals on the input lines of the input circuits on one of the inputboards are fed to a ten-way "or" gate 254. Should a signal on any one ofthe input lines to the gate 254, shown in FIG. 6b, from the lowerphotoelectric cell 94, shown in FIG. 6a, indicate that there is a pieceof sheet material between one of the wheels and the roller, an outputsignal is given from the gate on a skin detector output line 256 of theinput board. The skin detector output line of each of the input boardsis connected to a six-way "or" gate 258 on the scan board, as shown inFIG. 7. Should any signal indicating the presence of a skin between oneof the wheels and the glass roller be received on any one of the inputlines to the gate 258 a skin present signal is given on the output lines260,262 from the gate. The output line 260 leads to an "end of skin"detector circuit 264 and the output line 262 leads to a control circuit266. When a skin is in the machine and a signal indicating this is givenon the line 262, the control circuit 266 causes a signal to be given ona line 268. The signal on the line 268 is received on the line 246 ofthe control board, (see FIG. 7). When a signal indicating that a skinhas been fed into the illustrative machine is received on the line 246,shown in FIG. 8a, the signal passes through an alarm control 269 to askin counter 270 which records the feeding through of the skin andcauses the number of skins fed through the machine in the particularbatch being measured to be displayed in a display 272, shown in FIG. 8b,on the display unit.

When a skin is first fed into the machine, an output indicating thepresence of the skin is given on the line 260 which passes through theend of skin detector circuit 264, shown in FIG. 7. An output signalindicating that there is a skin in the machine is given on the line 274from the circuit 264. The signal from the line 274 is fed into an inputline 276 on an auxiliary board 275, shown in FIG. 10, and this signal onthe line 276 sets a latch 278 and causes signals to be sent to a gate280 to inhibit operation of the batch total count and to a gate 282 toinhibit operation of the grand total signal.

As hereinbefore mentioned, the latch 278 is set when a signal indicatingthat a piece of sheet material has been fed into the machine is receivedon the input line 276. Setting of the latch 278 sets the alarm circuitwhich is triggered by operation of any one of the microswitches 78,shown in FIG. 2. Should one of the wheels 46 of the machine having oneof the microswitches 78 associated therewith be rotated in the directionopposite the through feed direction a signal is emitted by the closureof the microswitch, the signal being received on the line 284 of theauxiliary board 275, shown in FIG. 10, a switch 286 is included in theline 284, so that the alarm circuit can be rendered inoperative ifdesired. Normally, however, the switch 286 is closed thus rendering thealarm circuits active. When a signal is received on the line 284 to thelatch 278, an alarm signal is emitted on a line 288 which operates anaudible warning device to draw the operator's attention to thesituation, and an alarm signal is emitted on the line 290. The line 290,shown in FIG. 10, is connected to an alarm input line 292 on the controlboard, shown in FIG. 9, leading to the alarm control 269. If an alarmsignal has been given on the line 290 the alarm control prevents thepassage of any signal from the line 246 to the output line 294 from thealarm control. Once the latch 278 has been set to the alarm condition byreceipt of a signal from one of the microswitches 78, the latch remainsin the alarm condition until a signal is received on the line 276indicating that a new skin has been put into the machine. However, thereis a slight delay on the signal going to the line 276 when a skin is fedinto the illustrative machine and thus the latch 278 is not reset to theclear condition until after a signal indicating that a new skin has beenput into the machine is delivered on the line 246; thus the alarmcontrol is not reset to permit such a signal to pass from the line 246to the line 294 in time to receive this signal; the insertion of the newskin therefore fails to activate the skin counter 270; in this way thepassage of the skin in respect of which an alarm signal was given by oneof the microswitches 78, is not recorded on the skin counter 270.

Assuming that the alarm control 269 is set in the condition in whichpassage of signals from the line 246 to the line 294 is permissible,when the trailing edge of a skin passes from between the last of thewheels between which and the glass roller the skin had been present, thesignal given on the output lines 260,262 from the "or" gate 258, shownin FIG. 7, changes and thus the signal on the line 246 and on the line294 changes. An output line 296 from the line 294, on FIG. 8a, isconnected to a line 298, shown on FIG. 10, on the auxiliary board. Thechange of signal occurring when the trailing edge of a skin passes frombetween the last wheel and the roller causes a batch counter andcomparator 300, shown in FIG. 10, to register a count, to increase therecorded batch total by one. It will thus be appreciated that the skincounter 270, shown in FIG. 8a, and thus the visible display of skincount are operated to increase the total when the leading edge of a skinfirst enters between one of the wheels and the glass roller but thebatch counter and comparator 300, is operated to increase the batchtotal by one when the trailing edge of a skin leaves the machine.Assuming, now, that during the course of measurement of the area of askin, a signal is received from one of the microswitches causingoperation of the alarm control 269, at the beginning of that skin, theskin counter 270 will have increased the displayed skin total by one;however, as the alarm control 269 will have been set during the passageof the skin through the machine, when an end of skin signal is receivedon the line 246 this will not be transmitted to the line 296 and thus nosignal will be received on the line 298, shown in FIG. 10, and thenumber of skins counted by the batch counter and comparator will not beincreased. However, when the next skin is inserted into the machine thelatch 278 will be reset (but too late to operate the skin counter);thus, for this new skin the skin counter 270 will remain at the countgenerated by the preceding skin. At the end of this next skin, however,because no alarm signal has been given on the line 292, the end of skinsignal will reach the line 296 and will thus be counted by the batchcounter and comparator 300 thus it is ensured that both the skin counter270 and the batch counter and comparator 300 only count the number ofskins which actually pass through the illustrative machine without analarm signal being given by one of the microswitches 78. An alarm signalon the alarm input line 292 which operates the alarm control 269 alsogoes by a line 293, shown in FIG. 8a, to the line 250 which resets thearea counter 138, the counters 212,216 and the extra pulse control 206,to zero; the LED displays 236, shown in FIG. 8b, are also set to zeroand operation of the counters will not recommence until a new skin isfed into the machine. Thus if the alarm signal is given by operation ofone of the microswitches the area of the piece of sheet material inrespect of which the alarm signal was given is not recorded nordisplayed on the display unit, nor is the passage of this piece ofmaterial through the machine recorded and in order to measure the areaof that sheet of material the sheet has to be passed through the machineagain.

The machine comprises a number of thumb-wheel switches 302, as shown inFIG. 10, which may be set by an operator, prior to insertion of a pieceof leather in the machine, to set the batch size to be counted by themachine, thus setting the circuits of the batch counter and comparator300 to the desired level. When the batch counter and comparator 300counts (by end of skin signals received on the line 298) that the numberof skins fed through the machine, since the previous batch total is oneless than the batch total set by the switches 302, an output signal isgiven on a line 304, through a line 306 to illuminate an indicator lamp308, shown in FIG. 8b, thus signalling that the next skin to passthrough the illustrative machine will be the one to complete the batch.When the counter and comparator 300 counts that the skin counter, sincethe last batch total, has again reached the batch total set by thethumb-wheel switches 302, a batch total signal is given on an outputline 310 from the comparator 300. This signal, after passing through adelay 312, shown in FIG. 10, passes through a gate 314 giving an outputon a line 316 and on a line 318. The output on the line 318 signals apulse generator 320 which in turn causes a signal to be sent on a line322 to open the gate 282 and to a gate 324. A batch total signal on theline 316 is received by a line 326 on the control board, shown in FIG.8a, this batch total signal resetting the skin counter 270 andassociated visual display 272, shown in FIG. 8b, to zero. A batch totalsignal on the line 316 is also connected to an input 328, shown in FIG.9, on the the test board, for a purpose to be described hereinafter.

A circuit 330, shown in FIG. 10, for detecting when all the thumb-wheelswitches are set at nought is arranged to cause a circuit 332 to renderthe batch total circuitry inoperative along with the test sequences tobe described hereinafter by preventing batch total signals passingthrough the delay 312 to the gate 314 and preventing the operation of adriver 334 for the indicator lamp 308, shown in FIG. 8b. Alternatively asetting of the thumb-wheel 302 in a machine otherwise similar to themachine to nought may render the batch total circuits inoperative butcause a full test sequence to be operated every twenty or forty skins(depending on the circuitry selected).

The machine furthermore comprises a switch (not shown) operated by apush button (not shown) which sends a signal on a line 336 to the gate280, shown in FIG. 10. Provided that the gate 280 is not prevented frompassing a signal through by a signal on the line 276 indicating that askin is in the machine, a signal leaves the gate 280 on a line 338 tothe gate 314. Receipt of a signal generated by the push-button switch onthe line 336 by the gate 314 causes a batch total signal to be given onthe line 316 which, as hereinbefore described, resets the skin counter270 to zero and is also supplied to the input 328 of a test board 339,shown in FIG. 9.

The machine also comprises a push-button operated switch (not shown) bywhich a signal may be given on a line 340 to the gate 282, shown in FIG.10. When this push-button is depressed to generate a signal on the line340, an output signal is given from the gate 282 on a line 342, thisoutput signal travelling to a buffer board (not shown) on which thetotal area of skins measured since the previous operating of this grandtotal push-button occurred, is stored, the signal causing this totalarea to be printed out as a grand total on a printer (not shown)attached to the machine. The grand total push-button is effective togenerate a grand total signal on the output line 342 from the gate 282only when the gate 282 is not inhibited by a signal on the line 276(when there is a skin passing through the machine) or a signal on a line344 (indicating that the machine is undergoing test) and only when asignal is present on a line 346 indicating that a batch total sequencehas just operated.

As hereinbefore mentioned the machine comprises test means by which thefunctioning of the machine in the correct manner may be checked. Themachine comprises means arranged to emit a test start signal, operativeonly when there is no sheet material between the wheels 46 and thesurface of the glass roller 14. The means arranged to emit a test startsignal may be manually operated, e.g. a manual test button or may beautomatic, circuitry of the machine being arranged to emit the teststart signal after the machine has carried out a particular sequence ofoperations. A selector switch 350, shown in FIG. 9, is provided whichmay be set by the operator in the position in which it is shown in FIG.8 of the drawings, in which position the test start signal is emittedautomatically as hereinafter described in the operation of the machine,or the switch 350 may be set in an off position (shown in dotted-line inFIG. 8 in which position no tests may be run. Finally the switch 350 maybe set in a manual position (indicated in FIG. 8 by chain-dot lines) inwhich tests may be initiated by operation of the manual test button ashereinafter described.

The machine, as hereinbefore mentioned, comprises a switch arranged toswitch the measurement unit from quarters of a square foot to squaredecimeters and vice versa. The output from the switch is received on aline 352, shown in FIG. 10, into the gate 324. If there is no leather inthe machine, operation of the selector switch causes an output to begiven from the gate 324 on a line 354, the output on the line 354 beingreceived on the line 222, shown in FIG. 8a, and setting a detector 356to the correct unit as well as operating the unit selector 220 ashereinbefore described. The line 354 is also connected to a line 358 onthe scan board, shown in FIG. 7, by which a comparator 360 is also setto the correct units as selected by the unit selector switch. When theunit selector switch is changed from one unit to the other unit anoutput is also given from the gate 324 on the line 346 to the gate 282to cause a grand total to be given of all the work which had passedthrough the machine since the previous grand total. Likewise an outputsignal is given from the gate 324 on the line 362 to the gate 280 tocause a signal to be sent on the line 338 thus to cause a batch totalsignal to be given on the line 316 from the gate 314 and cause a batchtotal to be printed of the batch accumulated since the previous batchtotal signal was given.

The gate 324 is, however, inhibited from giving any output signal on anyof the lines 354,346,362 whilst a skin is in the machine passing betweenthe wheels 46 and the roller 14. This is achieved by applying a signalfrom the output line 296, shown in FIG. 8a, from the control board, toan inhibit line 364 to the gate 324; shown in FIG. 10, the inhibitsignal on the inhibit line 364 prevents any output on the lines354,346,362 until the end of the skin has been reached at which time thesignal on the line 296 will change and remove the inhibit signal fromthe line 364 thus allowing the gate to be operative and give theappropriate output signals on the lines 354,346,362. Should an alarmsignal be given and the alarm control 269 prevent an output on the line296, the gate 324 will be operative but this will not cause any problemin view of the cancellation of all registers by the alarm signal.Operation of the manual test button sends a signal on a line 366 to thegate 280 and to a gate 368. Should a skin be present in the machine whena signal is given by the test button, a signal indicating this will bepresent on the line 276 and will prevent operation of the gate 280. Thesignal to the gate 368 on the line 366 sets the gate 368 in correctcondition. Assuming that there is no signal on the line 276 indicatingskin present, the signal on the line 366 to the gate 280 causes anoutput on the line 338 causing a batch total signal to be given on theline 316 with the effect herein described and causes a signal to begiven on a line 370 to the gate 368 to cause output signals to be givenon lines 372,374 from the gate 368. The signal on the line 372 isreceived on a line 376 on the test board 339 shown in FIG. 9, leading toa test override circuit 378. The test override circuit gives a test setsignal on an output line 380. The line 380 is connected to a line 382,shown in FIG. 7, on the scan board and the test set signal on the line382 is conducted to a first test control 384 of first test means of themachine. The output line 380 is also connected to a line 386 on the testboard leading to a second test control 388, shown in FIG. 9, of secondtest means of the machine. The line 380 is also connected to a line 390on the scan board leading to a latch 392 of third test means. The line380 is also connected to a line 500, shown on FIG. 8a, on the controlboard to a gate 502 to cause the counters 212,216,138 to be reset.Emission of a set test signal on the output line 380 to the lines382,386,390 causes the test controls 384,388 and the latch 392 to be setto the conditions in which the first, second and third test means areoperable to carry out the tests governed thereby. Operation of themanual test button also causes a signal on a line 503 on the controlboard, to a gate 442 to illuminate the test lamp on the display.

The output from the gate 368 on the line 374 is in the form of a testpulse which is received by a pulse input line 394 to the manual settingof the switch 350 on the test board, shown in FIG. 9. The test button348 is thus only effective to start a test sequence when the switch 350is in the manual position. The test sequence when the switch 350 is inthe manual position is the same as the test sequence when the switch 350is in the automatic position in which it is shown in FIG. 9 andoperation of the first, second, and third test means will be hereinafterdescribed assuming that the switch 350 is in the automatic position asshown.

Operation of the first test means will now be described. As hereinbeforementioned the first test control 384 of the first test means is situatedon the scan board shown in FIG. 7; operation of the first test meanscauses a check on each of the first, lower, photoelectric cells 94(electronically) and of the second photoelectric cells 92, bothoptically and electronically, through the circuitry of all of the inputboards to the scan board, thus to check that the input circuitry to thescan board test control 384 is working satisfactorily. The first testmeans is set in operation by supply of a start signal on a line 396 onthe scan board to the first test control 384. The signal is fed to theline 396 from a line 398 on the test board shown in FIG. 9. When theswitch 350 is in the manual position (shown in chain-dot line in FIG. 9)the test start signal is supplied to the line 398 and thus to the line396 and first test control 384, shown in FIG. 7, by operation of thetest push button, shown in FIG. 10, to give a test start pulse on theinput line 394 to the switch. However, in the automatic position of theswitch 350 in which the switch is shown in FIG. 9, the test start signalis fed to the line 398 from a line 400 on the test board, as shown inFIG. 9. The test start signal is fed to the line 400 from a line 402 onthe scan board leading from an output from the end of skin detectorcircuit 264.

When the signal on the output line 260 from the six-way "or" gate 258indicates that the trailing end of a skin has just passed from betweenthe wheels and the glass roller 14, the signals on the output lines fromthe end of skin detector circuit 264 are changed. One of the outputlines from the detector circuit 264 is the line 274 which is connectedto the line 276 on the auxiliary board, shown on FIG. 10. When a signalindicating the end of a skin is given on the line 274 the gates 280,282cease to be inhibited thus permitting the passing of a batch totalsignal as hereinbefore described. A line 404, shown in FIG. 7, leadsfrom the detector circuit 264 to the skin control circuit 266; when anend of skin signal is given by the detector circuit 264 on the line 404the control circuit prevents the passing of an output signal from thecontrol circuit 266 on the line 268; thus operation of the skin counter270 is prevented during operation of the first test means in carryingout the first test. A line 406 (from which the line 402 leads) connectsan output from the end of skin detector circuit 264 with the areacontrol 182. An end of skin signal on the line 406 prevents passage ofarea pulses through the area control 182 to the line 184, thuspreventing pulses from the wheels 46 being counted during operation ofthe first test. The signals on the line 404,406 are maintained duringoperation of the first test to prevent area pulses being passed by thearea control 182 and to prevent a skin signal being passed from the line262 to the line 268 by the control circuit 266. When the first test issatisfactory an output signal on a line 408, shown in FIG. 7, from thefirst test control 384 to the detector circuit 264 clears the detectorcircuit 264 thus removing the signals from the lines 404 and 406 so thatpassage of area pulses through the area control 182 is again possibleand passage of a signal from the line 262 to the line 268 through thecontrol circuit 266 is likewise possible.

As hereinbefore mentioned an end of skin signal on the line 402 providesthe test start signal to the first test control of the first test meansthus to start the first test (when the switch 350 is set in theautomatic position). When the test start signal is received on the line396 by the first test control 384 the output signal on the line 408 isalso supplied on a branch line 410 to a timer circuit 412, shown in FIG.7, thus causing an output signal to be given on a line 414 to the testcontrol 384 which causes a signal to be given on an output line 416 fromthe test control. Considering, for convenience, only one wheel 46 andassociated support member 58, this output signal on the line 416 issupplied to an input line 418 of the support member 58 of theillustrative machine shown in FIG. 6a (the output line 416 beingconnected to the input line of each of the support members 58 of themachine). The signal on the line 418 is supplied to a transistor 420connected with the first, lower, photoelectric cell 94; when the signalis supplied on the line 418 to the transistor 420 the photoelectric cell94 is forced to the condition which normally indicates the presence of apiece of sheet material in the machine and thus gives a read outputsignal on the output line 130 to the input line 132. The signal on theline 132 is transmitted to the end of skin detector circuit 264 on theline 260 but the detector circuit 264 (having previously detected an endof skin) is not in a condition to pass the signal through. Likewise theskin control 266 receives the signal from the line 132 on the line 262but is prevented from passing the signal through to the line 268 by thesignal on the line 404 as previously mentioned. Thus the skin countingcircuitry of the machine does not respond to the signal which wouldnormally indicate the presence of a skin, generated in the operation ofthe first test on the line 130.

The output line 416 is also connected to an input line 422 (one suchinput line being provided on each of the six input boards, see FIG. 6b.The signal on the line 422 goes to a second test control of the firsttest means and sends an output signal from the second test control 424to the gate 174 and, on a line 426 to the latch 166 (and the latch ofthe other nine input circuits of that input board). The signal to thegate 174 sets the gate for receipt of a signal on a line 428 from a gate430. The signal on the line 426 sets the latch 166 to a different statethus giving an output signal on the line 168 to a lamp driver 432thereby illuminating a light emitting diode fault indicator (one ofthese fault indicators being provided for each input circuit of theinput board). The latch 166 remains set in the test state to which ithas been set by the signal on the line 426 until a pulse is received onthe lines 134, 136 from the second photocell 92 associated with thatinput circuit. When a pulse is received on the line 136 a pulse is givenon the output line 164 from the pulse shaper 160 when the next clockpulse is received on the input circuit clock line 158 (the pulse shaper160 being in the read condition by virtue of the signal on the lines132,162 caused by the signal on the line 148). When an output pulse isreceived on the line 164 the latch 166, shown on FIG. 6b, is reset toits initial condition thereby removing the signal from the lamp driver432, thus extinguishing the light emitting diode fault indicator 434.Reversion of the latch 166 to its initial state caused by the pulse onthe line 164 causes a signal to be transmitted on an output line 436from the latch 166 to the gate 430. An output line (of which the outputline 436 is representative) is provided from each of the latches of theinput circuits of the control board, that is there are ten such outputlines going to the gate 430. When the signal indicating reversion of alatch to its initial condition is received on all of the ten outputlines 436 by the gate 430 a level change signal is given on the line 428to the gate 174 and is transmitted by the gate to the output line 176 tothe six-way "or" gate 178 of the scan board. When such a level changesignal is received by the gate 178 from all six of the input boards alevel change signal is given on the output line 180 from the gate 178thus indicating that the first test has been satisfactorily completed,the signal on the line 180 being fed by a line 438 to the first testcontrol 384. Receipt of this level change signal by the first testcontrol 384, shown in FIG. 7, causes a level change signal on the line408 which resets the end of skin detector circuit 264 to a condition inwhich it will again permit transmission of a signal indicating a newskin in the machine received on the line 260. Resetting of the detectorcircuit 264 removes the signals from the lines 404,406 thereby resettingthe area control 182 to a condition in which area pulses can passthrough from the line 180 to the line 184 and resetting the skin controlcircuit 266 to a condition in which a signal on the line 262 indicatingthe introduction of a new skin to the machine is passed to the line 268.

When the test start signal is received on the line 396 by the first testcontrol 384 a signal is also given on an output line 440 to the gate442, receipt of the signal by the gate 442 causes an output signal to begiven on a line 444, the line 444 being connected to a line 446 leadingto a lamp driver 448 which illuminates a test/fault indicator lamp 450on the display. This indicator lamp 450 remains illuminated until alltests being run by the machine have proved satisfactory. Thus, when thefirst test only is being run, when the test satisfactory level changesignal is given on the line 438, the first test control 384 removes thesignal from the line 440 and the gate removes the signal by which theindicator lamp 450 is illuminated, thereby extinguishing the lamp 450.

The timer circuit 412, shown on FIG. 7, is arranged to give the testsignal on the line 414 and thus on the line 416 for a predeterminedperiod (70 milliseconds in the machine) sufficient that at the possiblethroughput speed or speeds (i.e. the speed of rotation of the glassroller 14) of the machine every wheel 46 of the machine will, if themachine is operating correctly, have rotated through sufficient distanceto cause at least one pulse to be emitted by the photoelectric cell 92of each wheel on the output line 134. Thus, if the wheels and thecircuitry are operating correctly all of the latches of every inputcircuit of all the six input boards will be caused to revert to theirinitial conditions so that, as hereinbefore described, level changesignals will be received by the gate 178 from all of the input boards.However, should a pulse fail to be given by one of the photoelectriccells 92, for example because the wheel associated with that cell issticking or because that photoelectric cell is not functioningcorrectly, the latch 166 is associated with that photoelectric cell willnot receive a pulse to cause it to revert to its initial state and willremain in its test state maintaining the fault indicator light 434 ofthe appropriate input circuit illuminated. Furthermore, a level changesignal will fail to be given on the line from the input board inconnection with which the fault has occurred, to the gate 178 and thusno test correct level change signal will be received on the line 438 andthe first test control will therefore maintain the first test means in atest condition. In particular the signal will remain on the line 440maintaining the lamp 450 illuminated, and no reset signal will be givenon the line 408 so that the end of skin detector circuit will remain inthe condition in which it prevents passage of signals through the areacontrol 182 and the control circuit 266. The timer circuit 412 isarranged so that if no level change signal is given on the line 408(indicating that a test satisfactory signal has been received on theline 438 by the first test control 384) the 70 millisecond test signalis given on the line 414 after elapse of a second and the first test isthus run through again in the same manner as hereinbefore described.This recycling of the first test continues until the gate 178 receivessignals from all six input boards indicating that the operation of thefirst test is satisfactory.

Sometimes the first test may fail on its first cycle merely because apiece of dust has obscured one of the photoelectric cells 92 momentarilyduring the test or because one of the wheels 46 is caused to stickmomentarily by a piece of dirt during the test. Should such transitoryfaults cause initial failure of the first test, the first test will becompleted satisfactorily at the second attempt (under the control of thetimer circuit 412) and the further operation of the machine will not beimpeded. However, in the event that a persistent fault has occurred, thefirst test will continue to recycle as hereinbefore described untilaction is taken by the operator to correct the fault. The faultsindicator 434, shown in FIG. 6b, of the input circuit in which the faultis occurring will remain illuminated so that the area of the fault canreadily be located and corrected. As hereinbefore mentioned, when thefault has been corrected, the lamp 450, shown in FIG. 8b, will beextinguished and the machine can again be used to measure area. However,whilst the first test means indicates that the machine is in a faultycondition it is impossible for the machine to be used to measure thearea of any sheet material.

Second test means of the machine is now described. A test start signalmay be given, as hereinbefore mentioned, by operation of the test button(when the switch 350 is in its manual position), the test start signalbeing received on the input line 394 to a start line 452. When, however,the machine is operating with the switch 350 set, as shown in FIG. 9, inthe automatic position, a test start signal for the second test means istransmitted to the start line 452 via the input 328 on the test board,as shown on FIG. 9. The test start signal is given to the input 328 fromthe line 316. Such a test start signal is placed on the line 316 when,as hereinbefore described, a batch total signal is generated either byoperation of the batch total button to cause a signal on the line 336thereby to generate a test start signal on the line 316, or by a batchtotal signal generated by the counter and comparator 300, likewise tocause a test start signal on the line 316.

When a test start signal is received on the line 452 it is fed to thesecond test control 388 (of the second test means) to start second andthird test sequences of the machine. As will be recalled, a batch totalsignal is only given when no skin is passing through the machine. Thus,when the switch 350 is in the automatic position, a batch total signalwill be given when the end of skin signal is emitted in respect of thefinal skin making up the batch. As previously described, the emission ofan end of skin signal initiates a test start signal for the first testmeans. Thus, when the switch 350 is set in the automatic position, thefirst test means and the second test means are caused to run through thefirst, second, and third test sequences at the same time. The batchtotal signal will also be given to the line 452 when the switch is setin the automatic position when the machine is first switched on and,when switch 350 is in either the manual position or the automaticposition, when the switch to change the units of measurement between thequarters of the square feet and square decimeters and vice versa isoperated. Receipt of a test start signal on the line 452 by the secondtest control 388 sets the control 388 for receipt of signal from aproximity switch (not shown) associated with the glass roller 14, on aswitch line 454. The glass roller 14 has a metal block secured to theroller at one end portion thereof. The metal block (not shown) has acurved outer surface secured to an inner surface of the glass roller sothat the block rotates as the roller rotates. The metal block extendspartially round the periphery of the roller and has a radial leadingface and a radial trailing face. The peripheral distance between theleading and trailing faces of the metal block is determined by thedimensions of the roller as hereinafter described.

As hereinbefore mentioned a proximity switch (not shown) is associatedwith the roller 14; this proximity switch is situated adjacent the pathof travel of the metal block as the roller rotates. So that as theroller rotates the leading and trailing faces of the metal block willoperate the proximity switch sending signals on the line 454 to thesecond test control 388. The second test control is so constructed andarranged that, when a test start signal has been received on the line452, receipt of a signal on the proximity switch indicating first theleading face of the metal block and a further signal indicating thetrailing face of the metal block causes an output signal to be givenfrom the second test control 388 on a line 456 to operate a switch (notshown) and thereby switch off the lower light tube 26. Switching off ofthe lower light tube 26 stops light falling on the lower photoelectriccells 94 and thus causes an output signal to be given on the output line130 from each of the lower photoelectric cells 94 thus causing a signalto be given on the lines 260,262, as shown in FIG. 7, thus givingsignals on the lines 274,268 which would normally indicate the presenceof a skin in the illustrative machine. Thus, area pulses generated byrotation of the wheels pass through the area control 182 on the line 184to the gate 186. The area output pulses from the gate 186 appear on aline 458 as well as the output line 188. The line 458 is connected to athird test input line 460 on the test board.

The area signal output line from each of the six input boards, as wellas being connected to the gate 178, is connected to an input line on thetest board, shown in FIG. 9; the area signal output line 176 of the testboard shown in FIG. 6b is connected to an input line 462 for the secondtest sequence of the second test means. Each of these input lines leadsto a counter and comparator, each of the counters and comparators havingan output to an "and" gate 464; the input line 462 is connected to acounter and comparator 466 which in turn is connected by a line 468 tothe "and" gate 464. The third test input line 460 of the second testmeans leads to a counter and comparator 470 of the second test means.

After the lower light tube 26 has been extinguished by the signal on theline 456 emitted as a result of the signal on the switch line 454 ashereinbefore described, it is necessary to allow a slight elapse of timebefore initiating the test counts which form part of the second andthird test sequences of the machine. This elapse of time is necessary toallow the filament of the tube 26 to cool so that it emits insufficientradiation to activate any of the photoelectric cells 94; a period of onehundred milliseconds is sufficient for the light tube 26 used in themachine to reach this stage. The second test control 388 is therefore soconstructed and arranged as to initiate the test count of the secondtest means on receipt of a second start signal on the line 454 from theproximity switch; this start signal will be emitted by the proximityswitch when it detects the leading face of the metal block nextfollowing the signals from the switch which cause the light tube 26 tobe switched off by the signal on the line 456. When this start testcount signal is received on the line 454 by the second test control 388,a start signal is emitted from the test control 388 on a line 472, theline 472 being connected to the counter and comparator 470 causing thecounter and comparator 470 to count the pulses received on the line 460from the line 475 of the scan board, and to the counters and comparators466, causing them to start counting the signals received on their inputlines 462 from the output lines 176 of the input boards. The glassroller 14 rotates and the wheels 46 run on the surface of the glassroller emitting area pulses on the line 176 which, as previouslymentioned are finally received on the lines 460,462 and fed to thecounters and comparators 466,470. As the roller rotates signals willcontinue to be received on the line 454 from the proximity switch as thetrailing face and leading face of the metal block pass the proximityswitch. The second test control 388 is arranged to count the signalsreceived on the line 454, shown in FIG. 9, until the signals indicatethat the glass roller has revolved slightly over three times since thecount start signal was emitted on line 472; the test control 388 removesthe count signal from the line 472 when it receives from the line 454the signal denoting the trailing edge of the metal block received whenthe glass roller has rotated just over three revolutions. The distancebetween the leading face and trailing face of the metal block isselected so that, in rotating three revolutions plus the small distancetravelled from the leading edge of the metal block to the count stopsignal at the trailing edge of the metal block after the completion ofthe third revolution, the surface of the glass roller 14 on which thewheels 46 run has travelled through a preselected distance. Because inthe manufacture of the glass tubes, slight variations in diameter occur,tubes which are nominally of the same diameter may differ slightly fromthe nominal diameter. Thus, the diameter of each glass roller ismeasured before the roller is incorporated in the machine and a metalblock secured to the roller as hereinbefore described having suchdistance between its leading face and trailing face as to compensate forany departure from the nominal diameter. Thus, as the machine is setinitially to carry out the second and third test sequences by countingthe number of signals emitted as the running surface of the glass rollermoves through preselected distance, should the glass roller of themachine be broken, it can be replaced by another roller without makingany machine adjustments--the replacement roller having been measured andcalibrated by securing to it a metal block of the correct dimensions inthe manufacturer's factory. The glass roller is nominally about 155 mmin diameter. The leading and trailing faces of the metal block arespaced apart such that in rotating three and a bit times as hereinbeforedescribed the surface of the roller travels through 1470 mm. This shouldresult in every wheel running on the roller (provided the machine isoperating correctly) rotating so that the running surface of the wheelalso moves through 1470 mm. As the running surface of each wheel issplit, in effect, into 20 mm lengths this means that each wheel should,theoretically, produce about 73 pulses for this rotation but dependingon the position of each wheel when the start counting signal is given onthe line 472 and the position of the wheel when the stop counting signalis given, the actual number of pulses emitted by each wheel during thetest may differ from the theoretical number significantly.Statistically, it can be calculated that for a group of ten wheels, adifference in number of pulses received from the theoretical number ofup to 4% is within acceptable accuracy bounds. Each of the comparators466 is therefore programmed to compare the number of area pulsesreceived on the line 462 with this predetermined acceptable range. Inthe case of the present machine, the acceptable range is between 704 and767 pulses for each group of ten wheels. Should the number of pulsesarriving on the line 462 whilst the count signal is on the line 472 beoutside this acceptable range of 704 to 767, a fault lamp 474 which isilluminated when the count start signal is given on the line 472, shownin FIG. 9, remains illuminated and no output is given on the line 468 tothe gate 464, thereby indicating that the signals received on the line462 from the input board to which the line 462 is connected were outsidethe acceptable tolerance range.

Should the number of pulses received on the line 462 be within theacceptable range, however, the comparator 466 extinguishes the warninglight 474 and gives an output signal on the line 468. Should signals begiven on all of the line 468 leading to the comparator 464, therebyindicating that the number of signals received by all of the countersand comparators 466 were within the acceptable range an output signal isgiven on a line 476 to an "and" gate 478, shown in FIG. 9.

Similarly the counter and comparator 470 receives all of the signalsgenerated by a group consisting of all 60 of the wheels 46 whilst thecount signal is applied by the second test control 388 to the line 472and compares them with an acceptable range of numbers of pulses storedin the counter and comparator 470. Because the comparator 470 isreceiving signals from 60 wheels, a statistically acceptable toleranceis plus or minus 2% of the theoretical number of pulses (whereas thestatistically acceptable tolerance for groups of ten wheels is plus orminus 4% of the theoretical number of signals). When the count signal isfirst applied to the line 472 to start the counter and comparator 470 afault lamp 480 is illuminated. Should the number of pulses received onthe line 460 by the comparator 470 be within the acceptable range ofpulses (these pulses providing test signals) an output is given from thecomparator 470 extinguishing the fault lamp 480 and an output is givenfrom the comparator 470 on a line 482 to the gate 478. Receipt ofsignals on the lines 476,482 indicating that the number of pulsesemitted by the signalling means of each group of 10 wheels and by thegroup of wheels consisting of all the wheels of the present machine, arewithin the acceptable range and thus that each group of 10 wheels isfunctioning within the predetermined tolerances for groups of 10 wheelsand that the group of wheels consisting of all the wheels is functioningwithin the predetermined tolerance for the machine, a test satisfactorysignal is emitted from the gate 478 on a line 484 to the second testcontrol 388. When a test satisfactory signal is received on the line484, the signal on the line 456 is changed to switch the light tubes 26back on and the signal on the line 484 is transmitted on a line 486 to aline 488 on the scan board, the line 488 leading to the gate 442.However, should a test satisfactory fail to be received on either of thelines 476,482, no output signal is given on the line 484 and thus nosignal is given on the line 488 to the gate nor is a signal givenreilluminating the light 456. In the event that no test satisfactorysignal is given on the line 484, the second test control 388 allows thesecond and third test sequences of the second test means to run throughagain. This recycling of the second and third test sequences willcontinue until a test satisfactory signal is emitted from the gate 478on the line 484.

When the second test means is set in operation by the test start signal,the test/fault lamp 450 on the display board is illuminated via the gate442; this lamp will remain illuminated until a test satisfactory signalis received on the line 488 via the gate 442.

The fault lamp 474,480 associated with the group of wheels in respect ofwhich the fault is arising preventing the emission of the testsatisfactory signal by the second test means remains illuminated untilthe fault is rectified, thus facilitating the tracing of the fault.

The present machine further comprises third test means by which theoperation of the counter 138 and counters 212,216 is checked. A startsignal for the third test means is emitted on a line 488 leading fromthe line 452, a signal being received on the line 452 from the line 328or the line 394 depending on the setting of the switch 350. Thus thethird test means is set in operation to run a fourth test sequence ofthe machine at the same time as the second test means is set inoperation.

The line 490 is connected to a line 492 on the scan board (see FIG. 6),the line 492 leading to the latch 392 of the third test means. Receiptof the test start signal on the line 492 by the latch 392 sets the latch392 to a test condition in which a signal is given on an output line 494from the latch 392. The signal on the line 494 opens a gate 496 intowhich clock pulses are fed on a line 498 from the clock 140. The line494 is also connected to a line 500 on the control board, shown in FIG.8b, the line 500 being connected to an "or" gate 502. The signal on theline 500 from the line 494 causes the gate 502 to emit an output signalon a line 504 which resets the counters 212,216,138, and the extra pulsecontrol 206. The line 500 is also connected to the line 380 on the testboard so that when a test signal is given on the line 380 a signal islikewise given to the gate 502 to reset the counters 212,216,138 andcontrol 206 to zero as hereinbefore mentioned. Finally, the signal onthe line 494 is fed to the gate 186; the gate 186 is connected to thegate 496 by a line 506. When the signal on the line 494 has opened, thegate 496, clock pulses from the line 498 are fed through the gate 496 tothe line 506 and through the gate 186 to the output line 188 from thegate 186. Thus receipt of the test signal on the line 492 of the thirdtest means causes clock pulses to be fed on the line 188 to the areainput line 190 on the control board.

Receipt of the clock pulses from the line 188 by the line 190 causes thecounters 212,216 to count the clock pulses in the same way as the areapulses are counted. Depending on the setting of the units switch, pulsesare fed from the appropriate one of the counters 212,216, through theunit selector 220 to the counter 138 and counted on the counter, thefalse area represented by the pulses being displayed on the visualdisplays 236. The pulses counted by the counter 138 are also supplied tothe detector 356 which is set in appropriate condition to receive outputsignals from the counter 138 in the units to which the unit selectorswitch is set, by the signal on the line 222 from the line 354 by whichthe unit selector 220 is operated. The detector 356 is so constructedand arranged as to allow the counter 138 to operate until apredetermined area reading is reached; in the case of the presentmachine the predetermined area reading is 2222.2 (where the units aresquare decimeters) and 0222 and 2 quarters (where the units are quartersof a square foot). When the detector 356 detects that the counter hasreached the aforementioned predetermined test count, a stop signal isemitted from the detector 356, shown in FIG. 8a, on a line 308 which isconnected to a line 510 on the scan board.

When the signal from the latch 392 is given, as a result of the teststart signal on the line 492 of the third test means, clock pulses fromthe line 498 are fed through the gate 496 to an output line 510 (as wellas to the line 506). The clock pulses on the line 510 are fed to acounter 512 and counted. The pulses counted by the counter 512 aresupplied to the comparator 360 which compares the pulses counted by thecounter 512 with a preset number, the actual number being determined bythe units in which the present machine is set to measure, the comparator360, as shown in FIG. 7, being set to the appropriate condition forthose units by a signal from the line 354, shown in FIG. 10, on the line358.

When the stop signal is applied to the line 510 it is also transmittedon a line 514 to a gate 516. Receipt of the stop signal on the line 514by the gate 516 causes a test satisfactory signal to be given on a line518 if the signal on a line 520 from the comparator 360 to the gate 516indicates that the number of pulses counted by the counter 512 is withina predetermined tolerance of the number of pulses which should have beennecessary to cause the counter 138 to reach the false area total whichthe detector 356 is set to detect (in the present machine the number ofpulses necessary to reach the figure set in the detector 356 is about40,000 and the tolerance allowed is plus or minus 5 pulses). If, whenthe stop signal is received by the gate 516, the signal on the line 520indicates that the number of pulses counted is within the aforementionedtolerance, the output signal on the line 518 indicating that test foursequence of the illustrative machine is satisfactory is transmitted on aline 522 to the gate 442 thereby indicating that test four sequence issatisfactory. The signal is also fed to a sequencer 524, for a purposeto be described hereinafter.

Should the output on the line 520 from the comparator 360 when the stopsignal is received on the line 514 by the gate 516 indicate that thenumber of pulses counted by the counter 512 is outside the predeterminedtolerance no test satisfactory signal is given on the line 518, shown inFIG. 7, but a recycle test signal is given on an output line 526 fromthe gate 516 to the latch 392 of the third test means thus giving anoutput signal on the line 494 similar to the signal given on that linewhen the test start signal is received on the line 492. The signal onthe line 494 resets the counter 512 to zero, the signal beingtransmitted to the counter 512 on a line 528, opens the gate 496 so thatclock signals are again allowed to pass from the line 498 to the line506 and resets the counters 212,216,138 to zero by passage of the signalalong the line 500. Thus the fourth test sequence, as carried out by thethird test means, continues to recycle until a signal is given on theline 520, at the same time as a stop signal is received on the line 514,indicating that the number of pulses counted by the counter 512 iswithin the predetermined tolerances.

When the signals are received on the lines 440,488,522 indicating thatthe four test sequences under the control of the first, second and thirdtest means are all satisfactory, an output signal is given on the line444 to extinguish the lamp 450 on the display thereby indicating thatthe test sequence is finished and that the machine is satisfactory. Thislamp 450 will not be extinguished if any one of the tests indicates thatthere is a fault in the machine, until the fault has been rectified.Whilst the machine is in a faulty condition, the electronic circuitrywill not permit the machine to be used to measure area.

The third test means, as well as controlling the fourth test ashereinbefore described also provides a test for the printer circuits.Thus when the test satisfactory signal is given on the line 518 to thesequencer 524 a signal is transmitted on a line 530 from the sequencer524 to the control circuit 266, this signal causing a signal to be givenon the line 268 indicating the end of a skin. Receipt of this false endof skin signal sends a print command causing the printer to print thenumber shown by the display 236, that is the number at which the stopsignal was given on the line 510 by the detector 356. At the same timeas the false end of skin signal is given on the line 530 a test fourbatch total signal is given on a line 532, by the sequencer 524, thissignal being received from the line 532 on a line 534 on the auxiliaryboard, shown on FIG. 10, to the pulse generator 320. When the false endof skin signal starts the printer, a printer busy signal is given on aline 536 to the pulse generator 320 and this causes an output signal tobe given on the line 322 to reset the sequencer 524 causing a genuinebatch total signal to be given to the printer to cause it to print thegenuine batch total. Should the printer fail to print the correct outputon the test four batch total, this can be seen by the operator who isthen in a position to suspect that the genuine batch total of the batchwhich triggered the operation of test four, subsequently printed by theprinter, may be incorrect, due to a faulty operation of the printer orprinter circuit.

When an output signal is given from the gate 422 indicating that testsare satisfactory, a latch 538 from which the line 444 leads is caused togive an output signal also on a line 540. The line 540 is connected to aline 542 on the control board (FIG. 8) which in turn leads to a switch544; the signal on the lines 540,542 causes the switch 544 to give anoutput signal on a line 546 which is connected to a latch line 548 onthe display board, the signal on the line 548 resetting the memorydecoders 234 of the display to zero.

The present machine also comprises a skin alarm timer 550 on the scanboard, shown in FIG. 7. When a signal is received on the line 274 fromthe end of skin detector circuit 264, indicating that a piece of sheetmaterial has been fed into the machine, the signal on the line 274 isfed to the skin alarm timer 550. This signal sets the timer in operationand the timer is set to emit a signal on an output line 552 leading tothe gate 442. Should a preset time from the introduction of a skinelapse without an end of skin signal being given on the line 274 (theend of skin signal stopping the timer 550 and resetting it to zero), analarm signal is given on the line 552 to the gate 442 causing the faultsignal to be given on the line 444 which illuminates the indicator lamp450 thereby indicating to the operator that a fault has arisen. Thetimer 550 of the present machine is set to emit the alarm signal 40seconds after a skin has been introduced into the machine--a period of40 seconds is sufficient for even the largest of hides to be fed throughthe machine at the slowest through feed speed of the machine.

The electrical circuits of the machine also comprise means (not shown)by which, if the test board, shown in FIG. 9, is removed from themachine, the machine will be closed down. Likewise, if one of the inputboards is not present in the machine, the machine will likewise beclosed down.

The machine is so constructed and arranged that operation of the testpush button for carrying out any of the tests automatically, will notaffect the memory associated with the grand total (this memory will onlyprint out and be reset to zero on operation of the grand total pushbutton or when units are changed, at the permissible times of themachine cycle) but will print a batch total on the printer and reset thebatch total memory to zero.

When the machine has a plug in the foot switch socket on the line 238,the counter 138, shown in FIG. 8a, will continue to add the areas ofeach successive sheet of material fed through the machine until suchtime as the foot switch is operated which will clear the counters212,216,138, resetting them to zero. Even when the machine is operatedin the manual condition the number of articles passed through theillustrative machine is registered by the batch counter, shown in FIG.9, and the indicator lamp 308, shown in FIG. 8b, will be illuminatedwhen the last skin of the batch (as set by the thumb wheel switches 302)is passing through the illustrative machine.

To summarize the tests, the first test means provides a check of theinput circuitry as far as the scan board; the second test means teststhat each sub group of wheels (10 in the present machine) is functioningwithin the prescribed tolerances for a sub group of that size and teststhat the group consisting of all of the wheels of the machine (60 in thecase of the present invention is functioning within the prescribedtolerance for a group of that size; the third test means checks that thecounter circuits are operating correctly and also provides a visualcheck for the operator to determine whether or not the printer unit andassociated memories are operating satisfactorily; finally an alarm isprovided which indicates when no end of skin signal has been receivedfor a long period.

The test means and alarm of the machine give warnings and prevent use ofthe machine should any faults arise. In this way the machine providesmore consistently accurate results than hitherto known area measuringmachines because any fault which develops is quickly brought to lightfor rectification. Furthermore, the provision of warning lamps referredto earlier in this description facilitates tracing of any fault whichdevelops thus allowing it to be put right more quickly. Furthermore, themachine of the present invention does not require any recalibration onceit has left the factory; the ability of the machine to measure area towithin the predetermined accuracy is determined by the construction ofthe machine, in particular by the spacing apart of the ntoches and ofadjacent wheels to produce a suitable area matrix. Once this matrix hasbeen determined by the manufacturer of the machine, the electroniccircuitry requires no calibration to ensure that area is recorded.

We claim:
 1. A machine for measuring the area of sheet material, saidmachine comprising:a conveyor means comprising a conveyor surface forsupporting sheet material the area of which is to be measured and forconveying the sheet material through said machine in the operationthereof; a plurality of wheels disposed side by side across said machineand arranged to run on sheet material conveyed by said conveyor meansor, in the absence of sheet material, on said conveyor surface;detecting means, one associated with each wheel for detecting thepresence of a piece of sheet material between each wheel and saidconveyor surface; signalling means for signalling each time theperiphery of a wheel has been rotated through a unit distance and foremitting a signal to be summed should the output from said detectingmeans associated with that wheel indicate that a piece of sheet materialis present between the wheel and the conveyor surface; computing meansfor summing the signals from each wheel to indicate the area of a pieceof sheet material; means arranged to emit a test start signal; and testmeans actuated by the test start signal, to cause, in the absence ofsheet material, all of said detecting means to emit a signal which wouldnormally indicate the presence of sheet material for a predeterminedlength of travel of the conveyor surface such that each of thesignalling means associated with the wheels of a group of wheels shouldsaid machine be functioning correctly, emits a number of test signals,said test means comprises a test circuit including a comparator by whichthe total number of test signals emitted by the signalling means of saidgroup of wheels is compared with an acceptable range of numbers of testsignals which would be emitted in respect of said group of wheels whensaid machine is functioning within predetermined tolerances, said testmeans being so constructed and arranged as to indicate the event thatthe comparator signals that the total number of test signals emitted bythe signalling means of said group of wheels is not within theacceptable range of numbers of test signals.
 2. A machine for measuringthe area of sheet material as recited in claim 1, wherein said conveyormeans comprises a roller having a surface which provides the conveyorsurface for supporting sheet material.
 3. A machine for measuring thearea of sheet material as recited in claim 1, wherein said detectingmeans comprises:a first detector equally spaced from next-adjacent firstdetectors and arranged at one side of the path of travel of the sheetmaterial through said machine, to detect a beam of radiation directedtheretowards from a first radiation source arranged at the other side ofthe path of the sheet material so that the presence of sheet materialbetween said wheel and said conveyor surface breaks the beam ofradiation; each first detector is a photelectric cell and each firstradiation source is a source of light; a single radiation source isarranged to direct beam of radiation at all of the first detectors; eachfirst radiation source is rich in infra red radiation and, where asingle first radiation source is used to direct a beam of radiation atall of the first detectors, the first radiation source is a light tube.4. A machine for measuring the area of sheet material as recited inclaim 1, wherein said conveyor means comprises a roller which istransparent to the radiation, and the source of light is mounted insidesaid roller to direct a beam of radiation at the first detectors.
 5. Amachine for measuring the area of sheet material as recited in claim 1,wherein each of said wheels comprises a rim portion projecting generallyparallel with the axis of rotation of said wheel from the remainder ofthe wheel, and said first photoelectric cells mounted on means by whichthe wheel is supported within the radius of the rim portion and the rimportion is continuous and transparent to infra red radiation emitted bythe first radiation source, said first photoelectric cells beingoperated by infra red radiation.
 6. A machine for measuring the area ofsheet material as recited in claim 1, wherein said signalling meanscomprises a plurality of second radiation detectors, one associated witheach wheel, mounted on means for supporting the wheel within the radiusof the rim portion at one side of the rim portion, and a secondradiation source mounted at the opposite side of the rim portion todirect a beam of radiation towards said second detectors;said wheelcomprising alternate first and second portions, being comprised of anotched insert ring fitted in the rim portion, and arranged so that asthe wheel rotates the notched ring also rotates and intersects the beamof radiation from the second source; the material of said insert ringbeing opaque to the radiation emitted by said second radiation source;said second radiation source emitting light rich in infra red radiation,so that when one of the notches in the notched ring intersects the beam,radiation from said second source reaches said second detector but whensaid ring itself intersects the beam, radiation from said second sourceis prevented from reaching said second detector.
 7. A machine formeasuring the area of sheet material as recited in claim 6, wherein saidnotches are so spaced apart that as said wheel rotates the distancemoved by the running surface of said rim portion of said wheel from thepoint at which one of the notches intersects the beam of radiation fromsaid second source permitting it to reach said second detectorassociated with said wheel, said notch being aligned between the secondsource of radiation and the second detector, to the point at which thenext-adjacent notch in said notched ring intersects the second beam ofradiation and again permits the second beam to reach said seconddetector, is a unit distance.
 8. A machine for measuring the area ofsheet material as recited in claim 7, wherein said detecting meanscomprises first detectors of radiation arranged to detect a beam ofradiation directed theretowards by a first radiation source arranged atthe opposite side of the path of travel of sheet material through themachine, said test means causing all of said detecting means to emit asignal which would normally indicate the presence of sheet material byswitching off said first radiation sources.
 9. A machine for measuringthe area of sheet material as recited in claim 8, wherein said testmeans comprises a first comparator by which the total number of testsignals emitted by the signalling means of a group of wheels consistingof all of the wheels of the machine is compared with a first acceptablerange of numbers of test signals, and a plurality of second comparators,each associated with a group of wheels, the total wheels of the machinebeing divided into a number of such groups of equal size, by which thetotal number of test signals emitted by the signalling means of eachsuch small group of wheels is compared with a second acceptable range ofnumbers of test signals; anda first indicator which indicates whether ornot the total number of test signals received by the first comparator iswithin the first acceptable range and a number of second indicators, oneassociated with each of the smaller groups of wheels, to indicatewhether or not the total number of test signals received by each secondcomparator is within the acceptable range.